GM Caprice 1990-1993 Repair Guide

Oxygen Sensor


See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Oxygen sensor - non-heated (1-wire)


An oxygen sensor is used on all models. The sensor protrudes into the exhaust stream and monitors the oxygen content of the exhaust gases. The difference between the oxygen content of the exhaust gases and that of the outside air generates a voltage signal to the ECM. The ECM monitors this voltage and, depending upon the value of the signal received, issues a command to adjust for a rich or a lean condition.

There are 2 different oxygen sensors used: a heated oxygen (HO2S) and non heated oxygen sensor (O2S). The 1992-93 4.3L engine uses the heated sensor to achieve and maintain closed loop status. The sensor needs to operate at 600°F. (315°C) in order to become a semiconductor and produce a voltage output between 0.01-1 volt. A lower voltage output would indicate the leaner (higher oxygen content) exhaust emissions. A higher voltage reading would indicate a richer (lower oxygen content) exhaust emission.


The sensor may be difficult to remove when the engine temperature is below 120° F (48 ° C). Excessive removal force may damage the threads in the exhaust manifold or pipe; follow the removal procedure carefully.

  1. Locate the oxygen sensor. It protrudes from the center of the exhaust manifold at the front of the engine compartment (it looks somewhat like a spark plug).
  3. Disconnect the electrical connector from the oxygen sensor.
  5. Spray a commercial solvent onto the sensor threads and allow it to soak in for at least five minutes.
  7. Carefully unscrew and remove the sensor.
  9. To install, first coat the new sensor's threads with GM anti-seize compound No. 5613695 or the equivalent. This is not a conventional anti-seize paste. The use of a regular compound may electrically insulate the sensor, rendering it inoperative. You must coat the threads with an electrically conductive anti-seize compound.
  11. Installation torque is 30 ft. lbs. (42 Nm). Do not overtighten.
  13. Reconnect the electrical connector. Be careful not to damage the electrical pigtail. Check the sensor boot for proper fit and installation.